The main objective of this research is to understand how gastric acid secretagogues and secretory inhibitors regulate the secretion of hydrogen ions in the stomach. Techniques recently developed in our laboratories to isolate and purify parietal cells (95-100% pure) from rat and guinea pig gastric mucosae will be utilized in these studies. We propose to precisely define the presence or absence of specific receptors for acetylcholine, histamine, gastrin, and several secretory inhibitors in isolated cells. We will test the hypothesis that interaction of one secretagogue with its receptor will alter interactions of other secretagogues with their receptors thus leading to modulation of acid secretion. We also propose to fully test the hypothesis that cyclic nucleotides mediate the effects of agents that stimulate gastric acid secretion. Cholinergic, adrenergic, and histaminic agonists and antagonists as well as polypetide hormones (gastrin, secretin, glucagon, insulin, and cholecystikinin) and prostaglandins will be studied using these isolated cells. The effects of these agents on isolated parietal cell adenylyl cyclase, guanylyl cyclase, and cyclic nucleotide phosphodiesterases will be determined. Also the singular and combined effects of secretagogues and inhibitors will be tested upon cellular cyclic AMP and cyclic GMP content. The binding of these agents and their effects on cyclic nucleotide metabolism will be correlated with oxygen consumption and triglyceride and carbohydrate synthesis, storage and catabolism. This research will lead to a better understanding and description of the molecular mechanisms controlling gastric acid secretion.